Musannaf Ibn Abi Shayba 3:4686

Waki’ narrated to us, from ‘Uyaynah ibn ‘Abd al-Rahman, he said: I was with my father in the mosque, and he saw a man standing with his feet spread apart. He said: "Join one of them to the other. I have seen eighteen of the companions of the Prophet, may Allah bless him and grant him peace, in this mosque, and I have never seen any one of them do this at all."